Global CSS for an app with web components

I'm developing a web application that uses HTML 5 native web components. My problem is that I have a lot of common CSS for all of these and I use font awesome to have nice icons. Right now I put all my styles inside "/deep" shadow piercing but Chrome says : "/deep/ combinator is deprecated." Do you have any suggestions on how can I have global CSS and CSS libraries (like font awesome) available on the whole app ?